Siskiyou aster

(Symphyotrichum lanceolatum var. hesperium)

Conservation Status


No image available

  IUCN Red List

not listed


NNR - Unranked

SNR - Unranked


not listed

Wetland Indicator Status
  Great Plains

FACW - Facultative wetland


FAC - Facultative

  Northcentral & Northeast

FACW - Facultative wetland


Siskiyou aster (var. hesperium) is a 12 to 60 tall, erect, perennial forb that rises on a single stem from a long, slender, branched rhizome. It sometimes forms large, dense colonies.

The stem is erect, straight, stout, and grooved. It is unbranched below the middle. It is green at first, eventually becoming brown and woody near the base. Above the middle it usually has many, sometimes just a few, spreading, ascending branches. It is usually hairless toward the bottom and may have sparsely to moderately dense, longitudinal lines of short, white, spreading or curled hairs toward the top.

Basal leaves are stalkless. The leaf blades are thin, inversely lance-shaped or inversely egg-shaped, up to 3 long, and up to ¾ wide. They are tapered at the base, and rounded or angled at the tip. There is a short, sharp, abrupt point at the tip. The upper and lower surfaces are hairless. The margins are toothed with rounded, forward-pointing teeth, and have a fringe of hairs. Basal leaves are usually withered at flowering time.

Stem leaves are alternate. Lower stem leaves are stalkless or on short, winged, poorly differentiated leaf stalks (petioles). The petioles are winged and sheath the stem at the base. The leaf blades are linear lance-shaped to inversely lance-shaped, 2 to 6 long, and to ¾ wide. They are wedge-shaped or tapered and sometimes slightly expanded at the base, but they do not clasp the stem. They taper to a point at the tip. The upper and lower surfaces are hairless. The margins are shallowly toothed. The leaves become progressively smaller, narrower, and shorter-stalked as they approach the middle of the stem. Middle and upper stem leaves are untoothed. Upper stem leaves are stalkless, linear, and 1¼ to 4 long, not much smaller than the middle stem leaves. Lower stem and sometimes some of the larger middle stem leaves are withered by flowering time.

The inflorescence is a branched cluster (panicle) at the end of the stem. The primary branches of the panicle are relatively sparse, loosely ascending or spreading, and sometimes solitary or more often clustered near the end of the vegetative branch. The flower heads are closely spaced, appearing dense, on lateral, secondary branches. The heads are usually oriented in various directions, sometimes oriented toward the top of the branch. The flower heads are on 3 16 to 2 long flower stalks (peduncles). They are usually subtended by leaf-like appendages (bracts). The leaves on the flowering branches are often longer than the peduncles, but are much smaller than the upper stem leaves.

The individual flower head is medium-sized, ¾ to 1 in diameter. The whorl of bracts (phyllaries) at the base of the flower head form a cup-shaped, to ¼ long cup (involucre). The phyllaries are arranged in 3 to 5 appressed to slightly spreading, overlapping series. They do not have a spine-like tip. Phyllaries in the outer series are as long or longer than those of the inner series. There are 18 to 45 ray florets and 18 to 52 disk florets. The ray florets are in 1 or 2 series. They are to long and usually pale to dark purplish-blue, sometimes white. The disk florets are yellow at first, eventually becoming purple. The flowers are not fragrant.

The fruit is a dry seed capsule (cypsela) with a tuft of bristles (pappus) attached to the end. The cypsela is egg-shaped, gray to tan, and 1 32to 1 16 long. It has 4 or 5 longitudinal ribs. The pappus is white to off-white.




12 to 60


Flower Color




Similar Species


Eastern panicled aster (Symphyotrichum lanceolatum ssp. lanceolatum) heads are not subtended by large, leaf-like bracts. Phyllaries in the outer series are to as long as those of the inner series.


Moist. Stream banks, wet meadows, and ditches. Full sun to partial shade.




July to October




Distribution Map



3, 28.









  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (dicots)  
  Superorder Asteranae  


Asterales (sunflowers, bellflowers, fanflowers, and allies)  


Asteraceae (sunflowers, daisies, asters, and allies)  
  Subfamily Asteroideae  
  Supertribe Asterodae  
  Tribe Astereae (asters and allies)  
  Genus Symphyotrichum (aster)  
  Subgenus Symphyotrichum  
  Section Symphyotrichum  
  Species Symphyotrichum lanceolatum (white panicled aster)  
  Subspecies Symphyotrichum lanceolatum ssp. hesperium (Siskiyou aster)  

This and other asters were formerly place in the genus Aster. That genus was problematic, in that it did not include just one common ancestor with all of its lineal descendants and no others – it was not monophyletic. In 1994, the genus Symphyotrichum was resurrected to include most North American asters formerly in the genus Aster.

This is a variety of a subspecies, and some sources list it as Symphyotrichum lanceolatum ssp. hesperium var. hesperium. The ICN (International Code of Nomenclature for algae, fungi, and plants), the rules governing the naming of plant species, makes it clear that this is not correct. Following ICN rules, a taxa “may also be referred to” with the inclusion of the intervening name (in this case, “ssp. hesperium”), but that does not constitute a formal name.


Subordinate Taxa






Aster hesperius

Aster laetevirens

Aster lanceolatus ssp. hesperius

Aster hesperius var. laetevirens

Aster hesperius var. wootonii

Aster wootonii

Aster osterhoutii

Symphyotrichum hesperium

Symphyotrichum lanceolatum ssp. hesperium var. hesperium


Common Names


panicled aster

Siskiyou aster

tall white aster

western panicle aster

white panicle aster












Modified leaf at the base of a flower stalk or flower cluster.



Describing a leaf that wholly or partly surrounds the stem but does not fuse at the base.



A dry, one-chambered, single-seeded fruit, formed from a single carpel, with the seed attached to the membranous outer layer (wall) only by the seed stalk; the wall, formed from the wall of the inferior ovary and also from other tissues derived from the receptacle or hypanthium, does not split open at maturity, but relies on decay or predation to release the contents.



A whorl of bracts beneath or surrounding a flower or flower cluster.



Long, straight, and narrow, with more or less parallel sides, like a blade of grass.



A pyramidal inflorescence with a main stem and branches. Flowers on the lower, longer branches mature earlier than those on the shorter, upper ones.



The modified calyx composed of awns, scales, bristles, or feather-like hairs in plants of the Asteraceae family.



The stalk of a leaf blade or compound leaf that attaches the leaf blade to the stem.



An individual bract within the involucre of a plant in the Asteraceae family.



A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.



The lower part of the leaf that surrounds the stem.


Winged leaf stalk

A leaf stalk with a leaf-like or membrane-like extension along both sides.


Visitor Photos

Share your photo of this plant.

This button not working for you?
Simply email us at
Attach one or more photos and, if you like, a caption. Photos






Visitor Videos

Share your video of this plant.

This button not working for you?
Simply email us at
Attach one or more videos or YouTube links and, if you like, a caption.

Other Videos



Visitor Sightings

Report a sighting of this plant.

This button not working for you?
Simply email us at
Be sure to include a location.






Last Updated:

About Us | Privacy Policy | Contact Us | © 2021 All rights reserved.